Wind turbine generator systems generating electricity using wind power, which is natural energy, have been conventionally known. This type of wind turbine generator system includes, for example, like the wind turbine generator system 1 shown in FIG. 3, a rotor head 4 to which wind turbine blades 5 are attached, a main shaft coupled to the rotor head 4 so as to integrally rotate with the rotor head 4, a step-up gear coupled to the main shaft that rotates by means of wind power received by the wind turbine blades 5, and a generator driven by a shaft output from the step-up gear, which are provided in a nacelle 3 mounted atop a tower 2.
In the thus-configured wind turbine generator system 1, the rotation of the main shaft and the rotor head 4 provided with the wind turbine blades 5 that convert wind power to rotary power generates shaft output. The output of the shaft whose rotational speed is stepped-up by the step-up gear coupled to the main shaft is transmitted to the generator. Accordingly, the shaft output obtained by converting wind power to rotary power works as the driving source of the generator, and thereby electricity can be generated using wind power as the motive energy of the generator.
In the above-mentioned wind turbine generator system 1, for example, as shown in FIG. 14, equipment E such as the step-up gear, the generator, and a controller is disposed inside the nacelle 3. This equipment E generates heat during operation, which causes an increase in the internal temperature. Accordingly, the nacelle 3 is provided with a ventilator for cooling the inside, whose temperature is increased due to the heat generated by the equipment E, to prevent the equipment E from being damaged by an increase in temperature to a specified temperature or more.
This ventilator includes an air inlet 31 provided on the front face of the nacelle 3, an air outlet 32 provided on the upper portion of the rear of the nacelle 3, and a ventilation fan (not shown) provided at the air inlet 31. The front face of the nacelle 3, which is provided with the air inlet 31, is the position where the dynamic pressure of the air flowing outside is the maximum.
The above-mentioned air inlet 31 is provided with, for example, a louver 33 having a configuration as shown in FIG. 15. The louver 33 shown in the drawing has a channel structure for preventing infiltration of rainwater into the nacelle 3. Comparing the intake air flowing from the outside of the nacelle toward the inside of the nacelle and the exhaust air flowing from the inside of the nacelle toward the outside of the nacelle, the channel resistances (pressure losses Δp) in both flow directions are the same.
In addition, in a wind turbine generator system in which a generator is stored in a hermetically-sealed case, a cooling mechanism has been proposed for forcibly ventilating the inside of the case using an air inlet provided in the case at the bottom end face side of the generator and an air outlet provided at an end at the front face of the case and driving a fan disposed near the air outlet in the case (for example, see Patent Document 1).    Patent Document 1: Japanese Unexamined Patent Application, Publication No. SHO-58-65977 (see FIG. 2)